This invention relates to an improved method for the production of metal powder from solid material such as metal wire of rod.
Fine metal powders is being used increasingly in the manufacture of parts by powder metallurgical techniques. Many methods of making metal powders have been proposed. These include the atomization of molten metal by gas jets (Helin et al., U.S. Pat. No. 3,428,718) or by high pressure water (Huseby, Pat. No. 3,325,277); spraying molten metal into a vacuum to form discrete particles (Wentzell, Pat. No. 3,510,546); the vaporization of metal in a vacuum followed by condensation (Allen et al. Pat. No. 3,049,421); the fusion of metal by an electric arc followed by the formation of condensed droplets which may be forced out of the arc zone either by means of a gas stream (Lezberg et al. Pat. No. 2,795,819, Schoop, Pat. No. 1,133,508) or by centrifugal force either alone (Chisholm et al., Pat. No. 3,021,562, McMillan, Pat. No. 2,897,539) or coupled with the influence of the magnetic repulsion inherent in the arc (Bridger, Pat. No. 1,887,577); forming a molten surface on a metal rod and agitating the molten metal at ultrasonic frequency generated either by an ultrasonic transducer or by use of a high frequency electric current coupled with a strong direct current magnetic field (Newberry, Pat. No. 3,275,787).
In addition it is known to form glass beads by passing an electric current through a stream of molten glass to cause an arc and subjecting the stream in the area of the arc to the action of the magnetic field of an electromagnet (Guyer et al., Pat. No. 3,313,608). In this latter method the interaction of the magnetic field produced by the electrical current in the current-carrying glass and the magnetic field caused by the electromagnet causes an intermittent making and breaking of the arc which in turn agitates the stream and causes the formation of glass beads.
In several of these prior art devices the process is carried on either in the presence of an inert gas (Lezberg et al., Pat. No. 2,795,819, Chisholm et al., Pat. No. 3,021,562, Newberry, Pat No. 3,275,787) or in a vacuum (Wertzell, Pat. No. 3,510,546, Allen et al., Pat. No. 3,049,421, McMillan, Pat. No. 2,897,539).